Tools and methods for tissue removal

ABSTRACT

The present invention is directed to material removal instrument for forming cavities in interior body regions, particularly cavities in intervertebral discs and vertebrae. The instrument includes a cannula and a rotation mechanism disposed at least partially within the cannula. A cutting element extends from the rotation mechanism and impacts and dislocates tissue as the rotation mechanism is rotated within the body. Dislocated tissue with withdrawn from the body via the cannula.

TECHNICAL FIELD

This invention relates generally to tools and procedures for formingcavities in interior body regions, particularly in intervertebral discsand vertebrae, for diagnostic and therapeutic purposes.

BACKGROUND

Certain diagnostic and therapeutic procedures for treatment and removalof disc material require access to and/or formation of a cavity in aninterior body region, including the intervertebral disc. Theintervertebral disc includes a thick outer ring of elastic soft tissuematerial (annulus fibrosus) and an inner gel-like substance (nucleuspulposus). Healthy disc material helps maintain flexibility of the spineand acts as a shock absorber dissipating loads across the spine. Whenthe condition of the disc material deteriorates as a result of, forexample, degenerative disc disease, herniation, and/or injury, thepatient may suffer deformation of the normal alignment or curvature ofthe affected area of the spine, as well as chronic complications and anoverall adverse impact upon the quality of life.

Until recently, doctors were limited to treating such deterioration andrelated deformities with pain medications, bed rest, bracing or invasivespinal surgery. Surgical removal of the offending disc material can becompleted (e.g., discectomy) to provide a treatment element to the discspace (e.g., bone graft, filler material, etc.) and/or fusion ofadjacent vertebral bodies using metal screws/rods. Standard surgicalinstruments for removing and/or creating a cavity in the intervertebraldisc include chisels, disc cutters, rasps, pituitary rongeurs, scrapers,curettes, cobb elevators, sizers, broaches or the like. The surgicalprocedure for accessing the disc may depend upon patient anatomy and/ordisc/vertebral condition.

A common drawback of most systems for removing disc material is thatthey require significant dissection and muscle retraction to accommodatethe multitude tools needed for creating the cavity, leading to longerrecovery time for the patient. Accordingly, there remains a need in theart to provide a safe and effective apparatus and method for minimallyinvasive disc tissue detachment and removal.

SUMMARY

The present invention is directed to tools and methods for creatingcavities in a body, in particular, cavities in intervertebral discmaterial and cancellous bone. An aspect of the present disclosure isdirected to a material removal instrument. The material removalinstrument may include a cannula and a rotation mechanism. The cannulamay include a cannula bore and a cannula opening at a distal end of thecannula, where the cannula opening can provide access to the cannulabore. All or a portion of the cannula may be constructed from a rigid orflexible material. Flexibility can be achieved based on the materialproperties of the cannula, structural properties and/or modifications tothe cannula, and/or a linkage with another portion of the materialremoval instrument. The rotation mechanism may be disposed at leastpartially within the cannula. The rotation mechanism may include anelongated shaft having a central bore and an opening at a distal end ofthe elongated shaft providing access to the central bore. The centralbore of the elongated shaft may be used to provide irrigation to thecutting area. The central bore of the elongated shaft may be sized andconfigured to receive a guide wire to direct placement of the rotationmechanism. All or a portion of the rotation mechanism, including theelongated shaft, may be constructed from a rigid or flexible material.

Flexibility can be achieved based on the material properties of therotation mechanism/elongated shaft, structural properties and/ormodifications to the rotation mechanism/elongated shaft, and/or alinkage with another portion of the material removal instrument.Flexibility of the cannula and/or the rotation mechanism can be used toprovide steering/directional control when accessing the target area andduring removal of tissue. The elongated shaft may also include a centralbore

In one aspect, the rotation mechanism may also include projectionsextending from a portion of the elongated shaft and a blade extendingfrom an other portion of the elongated shaft. The blade may be used fordislocating material from a target area. At least a portion of the blademay extend from the cannula opening. The rotation mechanism may berotated within the cannula to cause the blade to dislocate material fromthe target area. The dislocated material may be drawn from the targetarea through the cannula bore.

Another aspect of the present disclosure is directed to a materialremoval instrument that may include a cannula and a rotation mechanism.The cannula may include a cannula bore and a cannula opening at a distalend of the cannula. The cannula opening may provide access to thecannula bore. The rotation mechanism may be disposed at least partiallywithin the cannula. The rotation mechanism may include an elongatedshaft and a thread extending from a portion of the elongated shaft. Thethread may be used for dislocating material from a target area. Thethread may include a flank having a leading side and a trailing side.The trailing side may have a flank angle less than 90° with respect to alongitudinal axis of the rotation mechanism. At least a portion of therotation mechanism may extend from the cannula opening. The rotationmechanism may be rotated within the cannula to cause the thread toimpact and dislocate material from the target area.

A further aspect of the present disclosure is directed to a materialremoval instrument that may include a cannula and a rotation mechanism.The cannula may include a cannula bore and a cannula opening at a distalend of the cannula. The cannula opening may provide access to thecannula bore. The rotation mechanism may be disposed at least partiallywithin and rotatable within the cannula. The rotation mechanism mayinclude an elongated shaft, a connection element, and a mass element.The connection element may be fixed to the elongated shaft. The masselement may be used for dislocating material from a target area. Themass element may be fixed to the connection element. Rotation of therotation mechanism may cause the connection element to move in adirection away from a longitudinal axis of the rotation mechanism.Rotation of the rotation mechanism may also cause the mass element torotate about the longitudinal axis of the rotation mechanism at adistance from the longitudinal axis. Rotation of the mass element maycause the mass element to impact and dislocate material from the targetarea.

Another aspect of the present disclosure is directed to a materialremoval instrument that may include a cannula and a cutting element. Thecannula may include a cannula bore and a cannula opening at a distal endof the cannula. The cannula opening may provide access to the cannulabore. The cutting element may be disposed at least partially within thecannula and attached to an inner element. The cutting element may expandradially from the cannula opening upon movement of the inner elementfrom a first position to a second position in a direction along alongitudinal axis of the cannula. The rotation of the cannula with thecutting element in the expanded position may cause the cutting elementto impact and dislocate material from a target area.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

The device is explained in even greater detail in the followingdrawings. The drawings are merely examples to illustrate the structureof preferred devices and certain features that may be used singularly orin combination with other features. The invention should not be limitedto the examples shown.

FIG. 1A is a perspective view of an example material removal instrument;

FIG. 1B is a partial perspective view of an example material removalinstrument;

FIG. 1C is a partial perspective view of an example material removalinstrument;

FIG. 1D is a partial perspective view of an example material removalinstrument;

FIG. 1E is a partial perspective view of an example material removalinstrument;

FIG. 1F is a partial perspective view of an example material removalinstrument;

FIG. 1G is a partial cross-section view of an example material removalinstrument;

FIG. 1H is a partial perspective view of an example material removalinstrument;

FIG. 2A is a cross-section view of an example blade;

FIG. 2B is a cross-section view of an example blade;

FIG. 3 is side views of example blades;

FIG. 4 is side views of example blade blanks;

FIG. 5 is a superior view of an example disc and inferior vertebralbody;

FIG. 6A is a side cross-section view of an example rotation mechanism;

FIG. 6B is a side cross-section view of an example rotation mechanism;

FIG. 6C is a side cross-section view of an example rotation mechanism;

FIG. 7A is a perspective view of an example rotation mechanism;

FIG. 7B is a perspective view of an example rotation mechanism;

FIG. 8 is a partial side view of an example rotation mechanism;

FIG. 9 is a partial side view of an example rotation mechanism;

FIG. 10 is a partial perspective view of an example rotation mechanism;

FIG. 11A is a partial perspective view of an example material removalinstrument;

FIG. 11B is a partial perspective view of an example rotation mechanism;

FIG. 12A is a partial side view of an example rotation mechanism;

FIG. 12B is a partial side view of an example material removalinstrument;

FIG. 12C is a partial side view of an example material removalinstrument;

FIG. 12D is a posterior view of an example material removal instrumentand vertebral bodies;

FIG. 13A is partial side view of an example rotation mechanism;

FIG. 13B is partial perspective view of an example rotation mechanism;

FIG. 13C is partial perspective view of an example cannula;

FIG. 13D is a partial side cross-section view of an example cannula;

FIG. 13E is a partial top cross-section view of an example cannula;

FIG. 13F is a partial perspective view of an example rotation mechanismand cannula;

FIG. 14A is a side view of an example connection element and masselement;

FIG. 14B is a partial side view of an example material removalinstrument;

FIG. 14C is a partial side view of an example material removalinstrument;

FIG. 14D is a partial perspective view of an example material removalinstrument;

FIG. 15A is a perspective view of an example connection element and masselement;

FIG. 15B is a partial end view of an example rotation mechanism;

FIG. 15C is a partial side view of an example rotation mechanism;

FIG. 15D is a partial perspective view of an example rotation mechanism;

FIG. 15E is a partial end view of an example rotation mechanism;

FIG. 15F is a partial perspective view of an example rotation mechanism;

FIG. 16A is a partial side view of an example rotation mechanism;

FIG. 16B is a side view of an example rotation mechanism;

FIG. 16C is a side view of an example rotation mechanism;

FIG. 17A is a partial side view of an example material removalinstrument;

FIG. 17B is a partial side view of an example material removalinstrument;

FIG. 17C is a partial side view of an example material removalinstrument;

FIG. 17D is a partial side view of an example material removalinstrument;

FIG. 17E is a partial side view of an example material removalinstrument;

FIG. 17F is a partial side view of an example material removalinstrument;

FIG. 17G is a partial top view of an example cutting element;

FIG. 18A is a partial side view of an example material removalinstrument;

FIG. 18B is a partial side view of an example material removalinstrument;

FIG. 18C is a partial side view of an example material removalinstrument;

FIG. 18D is a partial side view of an example material removalinstrument.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right”, “left”, “lower”, and“upper” designate direction in the drawings to which reference is made.The words “inner”, “outer” refer to directions toward and away from,respectively, the geometric center of the described feature or device.The words “distal” and “proximal” refer to directions taken in contextof the item described and, with regard to the instruments hereindescribed, are typically based on the perspective of the surgeon usingsuch instruments. The words “anterior”, “posterior”, “superior”,“inferior”, “medial”, “lateral”, and related words and/or phrasesdesignate preferred positions and orientation in the human body to whichreference is made. The terminology includes the above-listed words,derivatives thereof, and words of similar import.

In addition, various components may be described herein as extendinghorizontally along a longitudinal direction “L” and lateral direction“A”, and vertically along a transverse direction “T”. Unless otherwisespecified herein, the terms “lateral”, “longitudinal”, and “transverse”are used to describe the orthogonal directional components of variousitems. It should be appreciated that while the longitudinal and lateraldirections are illustrated as extending along a horizontal plane, andthat the transverse direction is illustrated as extending along avertical plane, the planes that encompass the various directions maydiffer during use. Accordingly, the directional terms “vertical” and“horizontal” are used to describe the components merely for the purposesof clarity and illustration and are not meant to be limiting

Certain examples of the invention will now be described with referenceto the drawings. In general, such embodiments relate to a materialremoval instrument for cavities in intervertebral disc material andcancellous bone.

FIGS. 1A-1G provide perspective views of example material removalinstruments 100. The example material removal instrument 100 can includea cannula 120 and a rotation mechanism 140. The rotation mechanism 140can include a shaft 142. The shaft 142 can define an elongatedcylindrical structure. In another example (not shown), the shaft 142 candefine an elongated structure with a cross-section having any suitableshape including, for example, elliptical, square, rectangular, or anyother regular or irregular shape. The shaft 142 can be constructed froma flexible material (e.g., polymers, Nitinol) or a rigid material. Anexample shaft 142 constructed from a stiff and/or rigid material caninclude structural modification (e.g., geometric cutouts or shapes) thatprovide an overall flexible behavior regarding cross forces. Theflexibility of the shaft 142 can also be achieved by a linkage (notshown) between the cutting surface 152 and the flanks 158.

The shaft 142 can include a blade 146 extending from the outer surfaceof the shaft 142 body. The blade 146 can extend in a radial directionfrom the outer surface of the shaft 142 along a length of the shaft 142in the longitudinal direction. Likewise, the blade 146 can extend fromthe distal end 148 of the shaft 142. An example blade 146 can have alength along the longitudinal axis of the shaft 142 of about 12 mm toabout 17 mm. An example blade 146 can have a thickness ranging fromabout 0.4 mm to about 2 mm.

The blade 146 can include a cutting surface 152 along the outerperimeter of the blade 146. The cutting surface 152 can be used fordislocating material from a target area within the intervertebral disc(e.g., nucleus and/or annulus material) and/or cancellous bone. Thecutting surface 152 can define a continuous edge as provided in FIG. 1E.The cutting surface 152 can also define an interrupted edge. Forexample, as illustrated in FIGS. 1A-1D, 1F and 1G, the cutting surface152 can include a plurality of grooves 154 to aid in removal of materialas the cutting surface 152 moves along/impacts the target area. Thegrooves 154 can break/cut the material into smaller fragments therebymaking them easier to transport away from the target area and out of thebody of the patient. FIGS. 2A and 2B, provide an axial cross-sectionview of example blades 146. As illustrated in FIG. 2A, the cuttingsurface 152 can include a curved or rounded surface terminating at asharpened point/edge. As illustrated in FIG. 2B, the cutting surface 152can include an angled or chamfered surface terminating at a sharpenedpoint/edge.

The blade 146 can also include a portion that is rotated around thelongitudinal axis of the rotation mechanism 140. For example, asillustrated in FIGS. 1A-1D, 1F and 1G, the blade 146 can form a helicalsurface rotating around the longitudinal axis of the shaft 142. Theangle of rotation/twist of the blade 146 can be determined to prevent ahammering effect on the interior disc/bone surface when the blade 146 isrotated. The hammering effect occurs when disc/bone material is impactedas a result of the height of the cavity created by the blade 146 varyingduring blade rotation. As a result, the angle of rotation/twist of theblade 146 can be determined such that the width/height defined by therotated blade 146 generally constant.

FIG. 3 provides an illustration of an example blade 146 rotated/twistedat various angles. Row A provides an example blade 146 with 0° of bladetwist. From left to right in FIG. 3, the blade 146 is shown at variousorientations. As the entire blade 146 is rotated between 0°, 45°, and90°, the height defined by the blade 146, when viewed from the side,varies significantly. For example, Row A provides an example blade 146having 0° of blade twist. At a 0° orientation, the blade 146 has anarrow height profile. The height profile increases drastically as theentire blade 146 is rotated through 45° and 90° orientation. It can beestimated that a blade 146 with 0° of blade twist can have a bladeheight that varies approximately 70%. Such a drastic variation in bladeheight can cause a hammering effect on opposing disk surfaces duringrotation of the blade 146.

Row B provides an example blade 146 having approximately 90° if bladetwist. From left to right in FIG. 3, as the entire blade 146 is rotatedbetween 0°, 45°, and 90°, the height defined by the blade 146, whenviewed from the side, can vary approximately 30%. This blade heightvariation can also cause a hammering effect on opposing disk surfacesduring rotation of the blade 146.

Row C provides an example blade having approximately 180° of bladetwist. From left to right in FIG. 3, as the entire blade 146 is rotatedbetween 0°, 45°, and 90°, the change in height defined by the blade 146,when viewed from the side, is minimal (approximately null). As a result,the hammering effect is minimal.

Accordingly, in the present disclosure, an example blade 146 can have ablade twist less than about 90°. Another example blade 146 can have ablade twist of at least about 90°. Another example blade 146 can have ablade twist of at least about 180°. In a further example, the blade 146can have a blade twist greater than about 180°.

The pre-twist/blank shape of the blade 146 can define any suitableregular or irregular shape. FIG. 4 provides an illustration of exampleblades 146 with various blank (pre-twist) shapes (Column 1). Forexample, Row A provides an example blade 146 having a blank defining arectangular shape with convex side edges that curve and extend radially.Row B provides an example blade 146 with a blank defining a rectangularshape with square corners and straight side edges. Row C provides anexample blade 146 with a blank defining a rectangular shape with concaveside edges that curve inward radially. The blank shape of the blade 146can also be designed to maximize the contact of the cutting surface 152with the target area. FIG. 4 illustrates the twisted blades 146 at aninitial position (Column 2) and the twisted blades 146 rotated 90°(Column 3). As illustrated in Column 3, the amount of cutting surface152 contacting the target area at a 90° rotation is greatest with theblade 146 design provided in Row C, a rectangular shape with concaveside edges.

As illustrated in FIGS. 1A, 1B, 1D, 1E and 1G, the shaft 142 can alsoinclude projections 156 extending from the outer surface of the shaft142 body. The projections 156 can form a helical (or spiral) surfaceextending around the shaft 142. The height of the projections 156 can beconfigured such that the rotation mechanism 140 is rotatable within thecannula 120. When rotated within the cannula 120, the shaft142/projections 156 can act as a conveyor (or screw pump) for movingdislocated material from the target area and through the cannula bore122. The projections 156 can include a plurality of flanks 158. When theflanks 158 come into contact with the dislocated material, rotation ofthe shaft 142/flanks 158 generates a force in the axial direction on thematerial.

As explained in more detail below with respect to FIG. 8, the pitchbetween various flanks 158 of the projections 156 can vary along thelength of the shaft 142 to provide for different efficiency in removingdislocated material and/or help control the axial forces on the rotationmechanism 140. The pitch can be adjusted to define the rate of materialremoval as well as the particle size of the dislocated material capableof being transported through the cannula 120. In an example rotationmechanism 140 the pitch is uniform along the length of the shaft 142. Inanother example, the pitch varies between various flanks 158. Similarly,the length of the projections 156 along the longitudinal axis of theshaft 142 can be adjusted to provide for different efficiency inremoving dislocated material and/or help control the axial forces on therotation mechanism 140. In an example rotation mechanism 140, theprojections 156 can extend from the shaft 142 along a portion of theshaft 142. In another example (not shown), the projections 156 canextend along the entire length of the shaft 142.

Another example rotation mechanism 140, illustrated in FIG. 1H, caninclude a plurality of blades 146 rotated around the longitudinal axisof the rotation mechanism 140 to form a plurality of helical surfaces.During operation, the blades 146 rotate around the longitudinal axis ofthe shaft 142. The blades 146 originate at a first terminal 164 andterminate at a second terminal 168. The first and second terminals 164,168 can be operatively coupled to the elongated shaft 142. As outlinedin more detail below, the rotation mechanism 140 and/or the cannula 120can be formed from a flexible or rigid material to aid in direction andplacement of the rotation mechanism at the target area.

The shaft 142 can include a central bore 160 and an opening 162providing access to the central bore 160. The opening 162 can be locatedat the end of the shaft 142, as illustrated in FIGS. 1 A-1H. In anotherexample (not shown), the opening 162 can be located on a lateral surfaceof the shaft 142. The opening 162 can define any suitable shapeincluding, for example, circular, elliptical, square, rectangular, orany other regular or irregular shape. An example rotation mechanism 140may include multiple bore openings 162. For example, a bore opening 162can be provided on each side of the blade 146. It is contemplated thatthe bore 160 can be used to provide irrigation to the target cuttingarea. The proximal end of the bore 160 can be operatively coupled to anirrigation source for providing irrigation at the bore opening 162. Theirrigation can dissipate heat generated between the rotation mechanism140 and the target area and/or heat generated between the rotationmechanism 140 and the cannula 120. The irrigation can also preventdislocated material (e.g., soft tissue, bone, blood, or otherinterstitial fluid/materials) from adhering to the blade 146,projections 156, or inner surface of the cannula bore 122. Theirrigation also aids in the flow of the dislocated material from thetarget area through the cannula 120. It is further contemplated that thebore 160 can be sized and configured to receive a guide wire to directplacement of the rotation mechanism 140. In another example (not shown),the shaft 142 can include a solid structure, without including a bore160.

As illustrated in FIGS. 1A-1D and 1F-1H, the rotation mechanism 140 canbe disposed within a cannula 120. The cannula 120 is sized andconfigured to permit rotation of the rotation mechanism 140. The cannula120 can also function as a torque transmission element with respect todislocated material passing through the cannula bore 122 and/or therotation mechanism 140. In an example rotation mechanism 140, rotationalmovement of the cannula 120 can be fixed. In another example, thecannula 120 can rotate in the same or opposite direction of the rotationmechanism 140. The cannula 120 can define an elongated cylindricalstructure. The cannula 120 can be constructed from a flexible material(e.g., polymers, Nitinol) or a rigid material. An example cannula 120constructed from a stiff and/or rigid material can include structuralmodification (e.g., geometric cutouts or shapes) that provide an overallflexible behavior regarding cross forces.

An example cannula 120 can have an outer diameter ranging from about 3mm to about 6 mm. In another example, the cannula 120 can have an outerdiameter ranging from about 5 mm to about 6 mm. In a further example,the cannula 120 can have an outer diameter of about 5.5 mm. The cannula120 can include a central bore 122 sized and configured to accommodatethe rotation mechanism 140. The inner diameter of the central bore 122can range from about 2 mm to about 5 mm. The cannula 120 can alsoinclude an opening 124 providing access to the central bore 122. Theopening 124 can be located on the rotation mechanism 140 such that atleast a portion of the blade 146 is provided access to the target areawhen the material removal instrument 100 is located within the patient.The opening 124 can be located at the end of the cannula 120, asillustrated in FIGS. 1A-D and 1F-1H. In this example, the rotationmechanism 140, including at least a portion of the blade 146, can extendfrom the cannula opening 124. In another example (not shown), theopening 124 can be located on a lateral surface of the cannula 120. Inthis example, the cannula opening 124 can be sized and located such thatat least a portion of the rotation mechanism 140, including at least aportion of the blade 146, extends from the cannula opening 124. Theopening 124 can define any suitable shape including, for example,circular, elliptical, square, rectangular, or any other regular orirregular shape.

In use, the material removal instrument 100 can remove bony materialand/or disc material between adjacent and/or within vertebrae. When usedfor removal of disc material (e.g., discectomy), disc access can begained via a posterior and/or posterolateral percutaneous,extrapedicular approach. If a guide wire is used, it can be insertedinto the disc. As provided in FIG. 5, an introducer cannula 102 can beslid over the guide wire and introduced into the disc space. An exampleintroducer cannula 102 can have an outer diameter of about 3 mm to about7 mm. The cannula 120 and rotation mechanism 140 can then be providedinto the disc space via the introducer cannula 102. The material removalinstrument 100 (cannula 120 and rotation mechanism 140) can be locatedsuch that the cannula opening 124 is proximate the target area withinthe disc. Once positioned at the target area, the rotation mechanism 140can be rotated within the cannula 120 causing the blade 146 to contactand dislocate disc material at the target area and thereby create acavity, e.g., within the disc space. In an example material removalinstrument 100, the proximal end 150 of the rotation mechanism 140 canbe operatively coupled to a source of rotation energy.

The dislocated material can be drawn into the cannula opening 124 andthrough the cannula bore 122. As outlined above, rotation of therotation mechanism 140 can create pumping action that urges thedislocated tissue into the cannula opening 124 and through the cannulabore 122 without the use of supplemental aspiration/suction. In anotherexample, the proximal end of the cannula bore 122 can be operativelycoupled to a suction device to aid in removal of the dislocated materialfrom the target area and/or the cannula bore 122.

The material removal instrument 100 can be withdrawn from the cavity anda treatment element can be provided to the disc space. The treatmentelement can include, for example, a filler material and/or an inflatablebody, such as those used for kyphoplasty. The filler material caninclude, for example, bone cement, bone chips, demineralized bone,and/or an implant.

FIGS. 6A-6C provide side cross-section views of another example materialremoval instruments 200. The example material removal instrument 200 caninclude a cannula 220 and a rotation mechanism 240. The rotationmechanism 240 can include a shaft 242. The shaft 242 can define anelongated cylindrical structure. In another example (not shown), theshaft 242 can define an elongated structure with a cross-section havingany suitable shape including, for example, elliptical, square,rectangular, or any other regular or irregular shape. As outlined abovewith respect to shaft 142, the shaft 242 can be constructed from aflexible material (e.g., polymers, Nitinol) or a rigid material. Anexample shaft 242 constructed from a stiff and/or rigid material caninclude structural modification (e.g., geometric cutouts or shapes) thatprovide an overall flexible behavior regarding cross forces. Theflexibility of the shaft 242 can also be achieved by a linkage (notshown) between the cutting surface 252 and the flanks 258.

The shaft 242 can include a central bore 260 and an opening 262providing access to the central bore 260. The opening 262 can be locatedat the end of the shaft 242, as illustrated in FIGS. 6A-6C. In anotherexample (not shown), the opening 262 can be located on a lateral surfaceof the shaft 242. The opening 262 can define any suitable shapeincluding, for example, circular, elliptical, square, rectangular, orany other regular or irregular shape. An example rotation mechanism 240may include multiple bore openings 262. It is contemplated that the bore260 can be used to provide irrigation to the target cutting area. Theproximal end of the bore 260 can be operatively coupled to an irrigationsource for providing irrigation at the bore opening 262. The irrigationcan dissipate heat generated between the rotation mechanism 240 and thetarget area and/or heat generated between the rotation mechanism 240 andthe cannula 220. The irrigation can also prevent dislocated material(e.g., soft tissue, bone, blood, or other interstitial fluid/materials)from adhering to the threads 256 or inner surface of the cannula bore222. The irrigation also aids in the flow of the dislocated materialfrom the target area through the cannula 220. It is further contemplatedthat the bore 260 can be sized and configured to receive a guide wire todirect placement of the rotation mechanism 240. In another example (notshown), the shaft 242 can include a solid structure, without including abore 260.

The shaft 242 can include a thread 256 extending from the outer surfaceof the shaft 242 body. The thread 256 can form a helical (or spiral)surface extending around the shaft 242. The thread 256 can extend fromthe shaft 242 along the entire length of the shaft 242. In anotherexample, the thread 256 can extend along only a portion of the length ofthe shaft 242. The thread 256 can include a cutting surface 252 alongthe outer perimeter of the thread 256 for dislocating material from thetarget area within the intervertebral disc (e.g., nucleus and/or annulusmaterial) and/or cancellous bone. As illustrated in FIG. 6C, the cuttingsurface 252 can include an edge extending towards the proximal end 250of the shaft 242. The example cutting surface 252 can be used todislocate material from the target area and help to retain thedislocated material behind the flanks 258 for during rotation of theshaft 242.

Rotation of the shaft 242 can cause the cutting surface 252 to contactand dislocate material in the target area. Similarly, rotation of theshaft 242 can cause the thread 256 to act as a conveyor for moving thedislocated material 270 from the target area towards the proximal end250 of the shaft 242 (similar to the projections 156 included in therotation mechanism 140).

The thread 256 can include a plurality of flanks 258. In another example(not shown), the thread 256 can include a single flank 258. Each flank258 can include a leading side 272 and a trailing side 274. Each flank258 can define a flank angle (α). For the purpose of this application,the flank angle (α) will be defined with respect to the trailing side274 of the flank 258 and a reference plane parallel with thelongitudinal axis of the shaft 242. In the example rotation mechanism240 illustrated in FIG. 6A, the flank angle (α) defined by the flank 258is approximately 90°. A thread 256 having a 90° flank angle (α) providesa single cutting direction perpendicular to the longitudinal axis of theshaft 242, a radial component (as represented by Arrow A). To provide acutting direction in the parallel to the longitudinal axis of the shaft242 (an axial component), the rotation mechanism 240 can include acannula 220 that functions as a shearing sleeve. As the dislocatedmaterial 270 is transported towards the proximal end 250 of the shaft242 and the cannula 220, the interface between the flank 258 and thecannula 220 can detach the material from the target location and/orrupture the material into smaller pieces. Because the interface betweenthe flank 258 and the cannula 220 provides an additional dislocationpoint for the material, it is not necessary that the cutting surface 252of the thread 256 be as sharp as when the cannula 220 is not used as ashearing sleeve.

In another example, illustrated in FIG. 6B, the flank angle (α) can bean angle less than 90°. For example, the flank angle (α) range betweenabout 30° and less than about 90°. In another example, the flank angle(α) can range between about 45° and less than about 90°. In a furtherexample, the flank angle (α) can be about 70°. With a flank angle (α)less than 90° can result in better retention and transport of dislocatedmaterial 270 via rotation of the thread 256. In another example (notshown), an example rotation mechanism 240 with a flank angle (α) lessthan 90° can include a cannula 220 functioning as a shearing sleeve, asdescribed above with respect to FIG. 6A.

During rotation, a thread 256 having a flank angle (α) less than 90°provides a cutting directions perpendicular to the longitudinal axis ofthe shaft 242, a radial cutting component (represented by Arrow A), anda cutting direction parallel to the longitudinal axis of the shaft 242,an axial cutting component (as represented by Arrow B). FIG. 7A providesa perspective view of the example rotation mechanism 240 illustratingthe radial (Arrow A) and axial (Arrow B) cutting components when theshaft # is rotated (Arrow Z). A third cutting direction can be providedby moving the shaft 242 in the lateral (side-to-side) or vertical(up-an-down) direction. As illustrated in FIG. 7B, rotation of therotation mechanism 240 (Arrow Z), provides a radial cutting component(Arrow A) and an axial cutting component (Arrow B). Movement of thedistal end rotation mechanism # in the vertical direction (Arrow Y)provides a lateral cutting component (Arrow C).

As outlined above with respect to the rotation mechanism 240 works toremove dislocated material from the target by rotation of the threads256 (similar to rotations mechanism 140 and projections 156). As therotation mechanism 240/threads 256 urge the dislocated material towardsthe proximal end 250 of the shaft 242, forces in the opposite directiondirect (“pull”) the rotation mechanism 240 in the direction towards thedistal end 248. That is, consistent with Newton's third law of motion,when the rotation mechanism 240/threads 256 exert a force (F1) on thematerial in the target area, the material simultaneously exerts a force(F2) on the rotation mechanism 240. These forces are generally equal inmagnitude and opposite in direction. This force on the rotationmechanism 240 can causes the shaft 242 to “crawl” forward in the targetarea making control of the rotation mechanism 240 challenging.

Varying the pitch between various flanks 258 of the thread 256 along thelength of the shaft 242 can help control the resultant axial forces onthe rotation mechanism 240 (including the forward force) and can controlthe efficiency in removing dislocated material. That is, the pitch widthcan be adjusted to adjust the force in the axial direction on thematerial (e.g., the thrust effect on the dislocated material particles)and thereby dissipate the forward force on the rotation mechanism 240.The pitch can also be adjusted to define the rate of material removal aswell as the particle size of the dislocated material capable of beingtransported from the target area. As provided in FIG. 8, the pitchbetween various flanks 258 can vary. For example, the pitch (P1) betweena first set of flanks can be less than the pitch (P2) between a secondset of flanks. In another example rotation mechanism 240, illustratedfor example in FIGS. 6A-6C, the pitch between various flanks 258 isuniform along the length of the shaft 242.

Varying the height of the flanks 258 along the length of the shaft 242can also be adjusted to control the resultant axial forces on therotation mechanism 240 and provide for different efficiency in removingdislocated material. In general, the height of the flanks 258 isconfigured such that the rotation mechanism 240 can pass through androtate within the cannula 220. FIG. 9 provides a partial side view of anexample rotation mechanism 240 located within the disc space between theadjacent vertebral bodies. As illustrated in FIG. 9, the height ofvarious flanks 258 can vary along the length of the shaft 242. Forexample, the height of the first flank 258A can be less than the heightof the second flank 258B, and the overall flank height (H) progressivelyincreases from the distal end 248 towards the proximal end 250. Theflank height can be configured such that the flanks 258 located towardsthe proximal end 250 of the shaft 242 are proximate the surface of thesuperior and/or inferior vertebral body while the flanks 258 at thedistal end 248 of the shaft 242 can impact and dislocate materialwithout coming into contact with bony components. In another examplerotation mechanism illustrated in FIGS. 6A-6C, the height of the flanks258 can remain constant along the length of the shaft 242.

Varying the length of the thread 256 along the longitudinal axis of theshaft 242 can also be adjusted to control the resultant axial forces onthe rotation mechanism 240 and provide for different efficiency inremoving dislocated material. In the example rotation mechanism 240illustrated in FIG. 11B, the thread 256 can extend from the shaft 242along a portion of the shaft 242. In another example illustrated inFIGS. 6A and 6B, the projections 156 can extend along the entire lengthof the shaft 142.

The axial forces on the rotation mechanism 240 can also be controlled bythe use of a housing surrounding a portion of the rotation mechanism240. As illustrated in FIG. 10, the housing can include a sleeve 280that partially covers the shaft 242 and the threads 256. The shaft 242can rotate within the sleeve 280. The sleeve 280 can include a first arm282 and a second arm 284 and a distal end 286. The shaft 242 canmatingly engage the distal end 286. In another example, the shaft 242 isindependent of the distal end 286. The open space between the first arm282 and the second arm 284 can provide the threads 256 access tomaterial at the target area. In the example rotation mechanism 240, wheninserted into an intervetebral space, the first arm 282 and the secondarm 284 can protect material adjacent to and/or associated the superiorand inferior vertebra, while providing cutting windows in the posteriorand anterior direction.

The rotation mechanism 240 can be disposed within a cannula 220. Thecannula 220 can be similar in form and function to cannula 120. Thecannula 220 is sized and configured to permit rotation of the rotationmechanism 240. The cannula 220 can be constructed from a flexiblematerial (e.g., polymers, Nitinol) or rigid material. An example cannula220 constructed from a stiff and/or rigid material can includestructural modification (e.g., geometric cutouts or shapes) that providean overall flexible behavior regarding cross forces. As outlined above,the cannula 220 can also function as a torque transmission element withrespect to dislocated material passing through the cannula bore 222and/or the rotation mechanism 240.

The cannula 220 can define an elongated cylindrical structure having anouter diameter ranging from about 3 mm to about 15 mm. In anotherexample, the cannula 220 can have an outer diameter ranging from about 5mm to about 6 mm. In a further example, the cannula 220 can have anouter diameter of about 5.5 mm. The cannula 220 can include a centralbore 222 sized and configured to accommodate rotation of the rotationmechanism 240. The inner diameter of the bore 222 can range from about 1mm to about 5 mm. The cannula 220 can also include an opening 224providing access to the central bore #. The opening 222 can be locatedwith respect to the rotation mechanism 240 such that at least a portionof the threads 256 is provided access to the target area when thematerial removal instrument 200 is located within the patient.

As illustrated in FIGS. 11A and 11B, the opening 222 can be located on alateral surface of the cannula 220. In this example, the cannula opening222 can be sized and located such that at least a portion of therotation mechanism 240, including at least a portion of the threads 256,extends from the cannula opening 224, thereby limiting cutting in thedirection of the opening 224. The opening 224 can define any suitableshape including, for example, circular, elliptical, square, rectangular,or any other regular or irregular shape. The cannula 220 can include asingle opening 224 or a plurality of openings 224 (not shown). Inanother example (not shown), the opening 224 can be located at the endof the cannula 220 and the rotation mechanism 240, including at least aportion of the threads 256 can extend from the cannula opening 224.

The cannula 220 can also be used to control the axial forces on therotation mechanism 240. As illustrated in FIGS. 11A and 11B, the cannula220 partially covers the shaft 242 and the threads 256. As provided inFIG. 11A, the opening 224 can be located on a lateral surface of thecannula and can define an elongated opening extending in both thelongitudinal and radial surfaces of the cannula 220. By providing anopening 224, only those portions of the thread 256 proximate the opening224 come in contact with material at the target area with acorresponding other portion of the thread 256 are not in contact withthe material, thereby the axial forces resulting from rotation of theshaft 242 and contact with material at the target area are reduced. Thecannula 220 can cover the distal end 248 of the rotation mechanism 240.By covering the distal end of the rotation mechanism 240, the cannula220 helps prevent axial force on the rotation mechanism 240 from drivingthe rotation mechanism 240 forward. Covering the distal end 248 of therotation mechanism 240 also helps prevent unintentionally removingexcess material and/or damaging unintended tissue.

In use, the material removal instrument 200 can remove bony materialand/or disc material between adjacent vertebrae. The cannula 220 androtation mechanism 240 can be provided into the disc/bone space. Thematerial removal instrument 200 (cannula 220 and rotation mechanism 240)can be located such that the cannula opening 224 is proximate the targetarea within the disc. Once positioned at the target location and therotation mechanism 240 operatively coupled to a source of rotationenergy, the rotation mechanism 240 can be rotated within the cannula 220causing the threads 256 to contact and dislocate disc material at thetarget location and create a cavity within the disc space.

The dislocated material can be drawn into the cannula opening 224 andthrough the cannula bore 222. As outlined above, rotation of therotation mechanism 240 and threads 256 can act as a conveyor (or screwpump) for moving dislocated material from the target area and throughthe cannula bore # without the use of supplemental aspiration/suction.In another example, the proximal end of the cannula bore 222 can beoperatively coupled to a suction device to aid in removal of thedislocated material from the target area and/or the cannula bore 222.

FIGS. 12A-12D provide partial views of another example material removalinstrument 300. The example material removal instrument 300 can includea cannula 320 and a rotation mechanism 340. The rotation mechanism 340can include a shaft 342. The shaft 342 can define an elongatedcylindrical structure. In another example (not shown), the shaft 342 candefine an elongated structure with a cross-section having any suitableshape including, for example, elliptical, square, rectangular, or anyother regular or irregular shape. As provided in FIG. 12A, the shaft 342can define a first portion 370 having a first diameter and a secondportion 372 having a second diameter. In another example rotationmechanism 340, the diameter of the shaft 342 can be constant along thelongitudinal length of the shaft 342. In a further example, the shaft342 can include cutouts and/or hinges to accommodate the mass element346 during delivery through the cannula bore 322.

The rotation mechanism 340 can also include a connection element 380fixed to the shaft 342 and a mass element 346 fixed to the connectionelement 380. The connection element 380 can comprise a flexible memberfor connecting the mass element 346 to the shaft 342. Example connectionelements 380 can include wires, threads, and/or sheets formed from aflexible material. Other example connection elements 380 can includepre-shaped highly elastic materials including, for example, Nitinol(NiTi) strips. The pre-shaped connection element 380 can be stressed ina deformed shape while within the cannula 420. Upon removal from thecannula 420, the pre-shaped connection element 380 can be restored toits original, undeformed shape.

As illustrated in FIGS. 12A-12D, the mass element 346 can have around/spherical shape. In another example the mass element 346 candefine any suitable shape including, for example, spherical, ellipsoid,cube, torus, cylindrical, or square, rectangular, or any other regularor irregular shape. The mass element 346 can include a cutting surface352 on the perimeter or surface of the mass element 346 for dislocatingmaterial from a target area within the intervertebral disc (e.g.,nucleus and/or annulus material) and/or cancellous bone. The cuttingsurface 352 can include sharp edges, a roughened surface, a blastedsurface, and/or any other form of abrasive surface and/or feature formedon or attached to the mass element 346. For example, as illustrated inFIGS. 12A-12D, the mass element 346 can include a round/cylindrical masshaving an abrasive surface for dislocating material from the targetarea. The mass element 346 can have a weight less than about 1 gram. Inanother example, the mass element 346 can have a weight of about 1 gram.In a further example, the mass element 346 can have a weight greaterthan about 1 gram. An example mass element 346 has uniform weightdistribution. In another example, the mass distribution of the masselement 346 is concentrated at the cutting surface 352.

As illustrated in FIG. 12B, the mass element 346 can be attached to theshaft 342 via the connection element 380 such that the rotationmechanism 340 (shaft 342, connection element 380, mass element 346) canbe inserted into the body/target area via the cannula 320.

The rotation mechanism 340 can extend from an opening 324 in the cannula320. Rotation of the shaft 342 can cause the connection element 380 andthe mass element 346 to move in a direction away from the shaft 342. Asillustrated in FIGS. 12C and 12D, during rotation of the shaft 342, theconnection element 380 extends in a direction away from the longitudinalaxis of the shaft 342. As the mass element 346 rotates around thelongitudinal axis of the shaft 342, it impacts and dislocates materialfrom the target area. The length of the connection element 380 anddimensions of the mass element 346 can be adjusted to define the maximumexcavation diameter (D) created by rotation of the shaft 342. Asillustrated in FIG. 12 C, the maximum excavation diameter (D) can begreater than the outer and/or inner diameter of the cannula 320.

The shaft 342 can be constructed from a flexible material (e.g.,polymers, Nitinol) or a rigid material. An example shaft 342 constructedfrom a stiff and/or rigid material can include structural modification(e.g., geometric cutouts or shapes) that provide an overall flexiblebehavior regarding cross forces. The example rotation mechanismillustrated in FIGS. 13A and 13B includes a shaft 342 constructed from aflexible material. An example shaft 342 constructed from a stiff and/orrigid material can include geometric cutouts or shapes that provide anoverall flexible behavior regarding cross forces (e.g. spring). Asprovided in FIG. 13A, the mass element 346 can be attached directly tothe flexible shaft 342 without the use of a connecting element 380. Inthe example rotation mechanism 340 illustrated in FIGS. 13A and 13B, theexcentric center of mass of the shaft 342 and mass element 346 canresult in an imbalance when rotating the shaft 342. If the surface ofthe elongated shaft 342 also includes a cutting surface 352 such thatthe elongated shaft 342 (in addition to the mass element 346) can impactand dislocate material, the imbalanced center of mass can create a coneshaped cavity at the target area.

Depending on the desired application and patient anatomy, it may bedesirable to vary the shape of the cavity. When using a flexible shaft342, the shape of the cavity can be varied by changing the shape of thecannula opening 324. For example, the shape of the opening 324 can bevaried as illustrated in FIGS. 13C-13F. The opening 324 can include arecessed portion 326 and a protruding portion 328 where the shape of theopening defines the rotation/path of the flexible shaft 342 and the masselement 346. In particular, the recessed portion 326 permits the shaft342 to rotate to a diameter (X₁) and the protruding portion permits theshaft 342 to rotate to a diameter (X₂), where X₂ is greater than X₁.

In another example material removal instrument 300 illustrated in FIGS.14A-14D, the connection element 380 can include a flexible strip ofmaterial having a mass element 346 attached to a portion of the strip.In the example rotation mechanism 340, the mass element 346 isintegrally formed on the connection element 380. For example, the masselement 346 can be formed at a folded portion of the connection element380. The mass element 346 can be located at a position on the connectionelement 380 that defines the greatest distance from the longitudinalaxis of the shaft 342 when the connection element 380 and mass element346 are in a deployed position (e.g., when the shaft 342 is rotating andthe connection element 380 is extended from the shaft 342). The lighter,thinner, and/or more flexible portions of the folded connection element380 can be located between the mass element 346 and the shaft 342. It isalso contemplated that the mass element 346 can be located at a positionon the connection element 380 that defines the greatest distance fromthe longitudinal axis of the shaft 342 when the connection element 380and mass element 346 are in an undeployed position. When the center ofmass of the mass element 346 can also define the greatest distance fromthe longitudinal axis of the shaft 342 and the resulting force thatmoves the mass element 342 away from the rotation axis is higher. Thatis, applying Newton's second law (F=ma), the centripetal force (F) onthe mass element 346 can be determined using the following formulaF=mω²r, where m is the mass of the mass element 346, co is therotational speed of the mass element 346, and r is the radius ofrotation (distance between the mass element 346 and the rotation axis).

Another example material removal instrument 300 is illustrated in FIGS.15A and 15F. The connection element 380 is a flat strip of flexiblematerial capable of being wrapped around the shaft 342. The mass element346 can include a sharpened spike or other edge/projection formed onand/or fixed to the surface of the connection element 380. Theconnection element 380 is shown in an undeployed configuration in FIGS.15B-15D. As the shaft 342 is rotated, centrifugal forces urge theconnection element 380/mass element 346 outwards with regard to therotation axis of the shaft 342, as illustrated in FIGS. 15E and 15F.Because the properties of the connection element 380 (width, thickness,material, pre-shaping, etc.) can alter the centrifugal forces on themass element 346 and/or the rotational speed of the shaft 342, theexcavation diameter of the cavity can be adjusted.

Another example material removal instrument 300 is illustrated in FIGS.16A and 16B. To increase the cutting performance of the rotationmechanism 340 (i.e., amount of cut or detached material per unit oftime), the rotation mechanism 340 can including a plurality of masselements 346. When only one mass element 346 is used, a disc-like cavityis created (see FIG. 16C). To enlarge the cavity, the rotation mechanism340 must be moved in the axial direction (distance “a” in FIG. 16C),thereby creating a cylindrically-shaped cavity. When multiple masselements 346 are used, the same amount of axial movement (distance “a”in FIG. 16B), results in larger cavity than the single mass element 346cavity. Moreover, if a single mass element 346 detaches disc material ata certain rate (e.g., grams per second), multiple mass elements 346 candetach more disc material at a greater rate (assuming that the source ofrotational energy driving the rotation mechanism 340 can maintain aconstant turning speed).

As illustrated in FIG. 16A, mass elements 346 can be provided atshifted/offset locations along opposite sides of the length of the shaft342. In another example (not shown), the mass elements 346/connectionelements 380 can extend from the shaft 342 at mirrored positions alongthe length of the shaft 342. In another example illustrated in FIG. 16B,multiple mass elements 346 extend from one side of the shaft 342. In afurther example, a plurality of mass elements 346 can extend from anylocation around the perimeter (diameter) of the shaft 342. The rotationmechanism 340 can include an even or odd number of mass elements 346.The mass of each of the mass elements 346 can vary, or the mass can beconstant for each of the plurality of mass elements 346. The size and/orshape of each of the mass elements 346 and connection elements 380 canvary, or the size and/or shape can be constant for each of the pluralityof mass elements 346.

The rotation mechanism 340 can be disposed within a cannula 320. Thecannula 320 can be similar in form and function to cannula 120 andcannula 220, as outlined above. The cannula 320 can include a centralbore (not shown) sized and configured to accommodate rotation of therotation mechanism 340. The cannula 320 can also include an opening 324providing access to the central bore 322. The opening 324 can be locatedon the cannula 320 such that the rotation mechanism 340 (including themass elements 346) is provided access to the target area when thematerial removal instrument 300 is located within the patient. Thecannula 320 can be constructed from a flexible material (e.g., polymers,Nitinol) or a rigid material. An example cannula 320 constructed from astiff and/or rigid material can include structural modification (e.g.,geometric cutouts or shapes) that provide an overall flexible behaviorregarding cross forces.

In use, the material removal instrument 300 can remove bony materialand/or disc material between adjacent vertebrae. As illustrated in FIG.12B, the cannula 320 and rotation mechanism 340 can be provided into thedisc/bone space in an undeployed configuration. The cannula opening 324is proximate the target area within the disc/bony material. As providedin FIGS. 12C and 12D, the rotation mechanism 340 can be adjusted toextend from the cannula opening 324 at the target location. The rotationmechanism 340/shaft 342 can be operatively coupled to a source ofrotation energy causing the rotation mechanism 340 rotate. An examplerotation mechanism can rotate at speed raging from about 1,000 rpm toabout 20,000 rpm. Centrifugal forces resulting from the rotation of theshaft 342 force the mass element 346 and the connection element 380 in adirection away from the axis of rotation (i.e., the longitudinal axis ofthe shaft 342). The rotation of the shaft 342 also causes the masselement 346 to rotate about the longitudinal axis of the shaft 342 at anangular velocity and in a generally circular trajectory. As the masselement 346 is rotated about the axis of the shaft 342, the inertia andtrajectory of the mass element 346 cause the cutting surface 352 tocontact and dislocate disc material from the target location. Therequired rotational speed can be determined based on the weight of themass element 346 and the distance between the center of the mass elementand the axis of rotation.

As illustrated in FIG. 12C, the rotating mass element 346 can define adiameter (D) of rotation that determines the size of the cavity. Thediameter (D) can be defined by the length of the connection element 380and the size of the mass element 346. The flexibility/resistance of theconnection element 380 can also influence the diameter (D). For example,a flexible connection element 380 can fully expand into the disc spacealong the length of the connection element 380. In another example usinga semi-flexible connection element 380, the resistance of the connectionelement 380 can resist full expansion during rotation. The length and/orflexibility of the connection element 380 and the size of the masselement 346 can be provided such that the diameter (D) of rotation issimilar to the maximum disc height between superior and inferiorvertebral bodies. Likewise, the length and/or flexibility of theconnection element 380 and the size of the mass element 346 can beprovided such that the diameter (D) of rotation is greater than theouter diameter of the cannula 320.

As illustrated in FIG. 12D, the shaft 342 can be moved in the axialdirection to cause the mass element 346 to advance within the discmaterial and thereby remove additional material, enlarging the cavity.Likewise, the shaft 342 and/or cannula 320 can be moved in the lateraland/or vertical direction to remove to cause the mass element 346 toimpact additional disc material and enlarge the cavity in the lateraland/or vertical directions.

FIGS. 17-18 provide partial side views of other example material removalinstruments 400. The example material removal instrument 400 can includea cannula 420, a cutting element 446, and an inner element 480 attachedto the cutting element 446. The cutting element 446 can be disposedwithin the cannula 420. The cannula 420 can be similar in form andfunction to cannula 120, cannula 220, and cannula 320, as outlinedabove. The cannula 420 can be constructed from a flexible or rigidmaterial. The cannula 420 can include a central bore (not shown) sizedand configured to accommodate the cutting element 446 and inner element(not shown). The cannula 420 can also include an opening 424 providingaccess to the central bore. The opening 424 can be located such that atleast a portion of the cutting element 446 is provided access to thetarget area when the material removal instrument 400 is located withinthe patient.

As illustrated in FIGS. 17A, 17B and 17F, the cannula 420 can include asingle opening 424. In another example, the cannula 420 can include aplurality of openings 424 located around the around the outer surface ofthe cannula 420. For example, as illustrated in FIGS. 17C-17E, thecannula 420 can include two openings 424 provided on opposite sides ofthe cannula 420. The opening 424 can be located on a lateral surface ofthe cannula 420.

In another example illustrated in FIGS. 18A and 18B, the opening 424 canbe located on the end surface at the distal end 448 of the cannula 420.The opening 424 can define any suitable shape including, for example,circular, elliptical, square, rectangular, or any other regular orirregular shape.

The cutting element 446 can include a flexible blade and/or wire. Aportion of the cutting element 446 can be fixed to the inner elementsuch that movement of the inner element expands the cutting element 446radially through the cannula opening 424. The expanded cutting element446 can define an outer diameter greater than the outer diameter of thecannula 420. For example, the expanded cutting element 446 can define anouter diameter greater than the outer diameter of the cannula 420 byabout 1 mm to about 24 mm. That is, the cutting element 446 can expandradially from the outer surface of the cannula 420 from about 2 mm toabout 12 mm.

In an example material removal instrument 400, movement of the innerelement in the direction along the longitudinal axis of the cannula 420applies a force on the cutting element 446 expanding the cutting element446 radially through opening 424. In one example illustrated in FIGS.17A-17E, the proximal end of the cutting element 446 can be fixed to theinner element such that movement of the inner element in a directiontowards the distal end 448 (Arrows A in FIG. 17E) of the cannula 420expands the cutting element 446 radially through the opening 424.

In another example illustrated in FIGS. 17F and 17G, radial expansion ofthe cutting 446 can be controlled by changing the geometry of thecutting element 446. For example, the profile of the cutting element 446can be narrowed in the portions where deformation/radial expansion isdesired. As illustrated in FIG. 17G, the profile of the cutting element446 can be narrowed by including recesses 452 on the side portions ofthe cutting element 446. It is contemplated that the recesses 452 canhave a square, curved, or any regular or irregular shape.

In another example illustrated in FIGS. 18A and 18B, the inner elementincludes a central shaft 482 and end cap 484. The proximal end of thecutting element 446 can be coupled to the cannula 420 and the distal endof the cutting element 446 can be coupled to the end cap 484. Movementof the central shaft 482 in a direction towards the proximal end 450 ofthe cannula 420 applies a force on the cutting element 446 expanding thecutting element 446 radially through opening 424. In a further exampleillustrated in FIGS. 18C and 18D, the central shaft 482 and/or end cap484 can be rotated around the longitudinal axis of the central shaft482. The proximal end of the cutting element 446 can be coupled tocannula 420 and the distal end of the cutting element 446 can be coupledto the end cap 484 such that rotation of the central shaft 482/end cap484 causes the cutting element 446 to rotate around the central shaft482 and form a helical cutting surface.

As outlined above, the cannula 420 and the elongated shaft 424 can bothbe constructed from a flexible material (or a material exhibitingflexible response). A cannula 420 and/or shaft 424 constructed from aflexible material allows for steering when accessing the target area.Flexibility can also increase the range of motion of the materialremoval instrument 400.

In use, the material removal instrument 400 can remove bony materialand/or disc material between adjacent vertebrae. The cannula 420,including the cutting element 446, can be provided into the disc/bonespace such that the cannula opening 424 is proximate the target area.Once positioned at the target area, the cutting element 446 can beexpanded radially from the opening 424. The cannula 420 can beoperatively coupled to a source of rotation energy. Rotation of thecannula 420 causes the expanded cutting element 446 to contact anddislocate disc material at the target location and create a cavitywithin the disc space. The cavity can be expanded by moving the rotatingcannula 420/cutting element 446 axially, laterally, and/or verticallywithin the disc space.

It should be noted that specific features of the various embodimentsdisclosed herein can be performed manually by user-applied forces or,alternately, utilizing specialized motors/power sources. For example,rotation of the various components of the rotation mechanism 100, 200,300 and/or cannula 420 can be performed manually by a surgeon.Conversely, rotation of the various components of the rotation mechanism100, 200, 300 and/or cannula 420 can be performed by motorizedcomponents that may utilize, in certain implementations, microprocessorsor other guidance systems to coordinate the rotation speed and locationof the cutting surface to optimally form the cavity within the targetbody.

It is contemplated that each of the rotation mechanisms 140, 240, 340and cannula 420 can each include a central bore. The central bore can beused to provide irrigation to the cutting area. The central bore can beoperatively coupled to an irrigation source for providing irrigation tobore openings provided at the distal ends of the rotation mechanisms140, 240, 340 and/or cannula 420. The irrigation can be provided todissipate heat generated between the rotation mechanism 140, 240, 340and/or cannula 420 and the target area. The irrigation can alsodissipate heat generated between the rotation mechanism 140, 240, 340and/or cannula 420 and the cannula 120, 220, 320 and/or the introducercannula 102. The irrigation can also prevent dislocated material (e.g.,soft tissue, bone, blood, or other interstitial fluid/materials) fromadhering to the blade, projections, threads, cutting surface, masselement, cutting surface, and/or inner surface of the cannula boreand/or introducer cannual included in any one of the material removalinstruments 100, 200, 300, 400. The irrigation can also aid the flow ofthe dislocated material from the target area through the cannula 120,220, 320, 420. It is further contemplated that the bore included in eachof the rotation mechanisms 140, 240, 340 and cannula 420 can be sizedand configured to receive a guide wire to direct placement of therotation mechanism 140, 240, 340/cannula 420. An example guide wire caninclude a Kirschner wire (K-wire).

It is also contemplated that the cannula 120, 220, 320, 420 for each ofthe described material removal instruments 100, 200, 300, 400 canexhibit flexible behavior. All or a portion of the cannula 120, 220,320, 420 may be constructed from a rigid or flexible material.Flexibility can be achieved based on the material properties of thecannula 120, 220, 320, 420, structural properties and/or modificationsto the cannula 120, 220, 320, 420, and/or a linkage with another portionof the material removal instrument. Similarly, all or a portion of therotation mechanisms 140, 240, 340 for each of the described materialremoval instruments 100, 200, 300, 400 can also exhibit flexiblebehavior. In particular, the elongated shaft 142, 242, 342 may beconstructed from a rigid or flexible material. Flexibility can beachieved based on the material properties of the rotation mechanism 140,240, 340/elongated shaft 142, 242, 342, structural properties and/ormodifications to the rotation mechanism 140, 240, 340/elongated shaft142, 242, 342, and/or a linkage with another portion of the materialremoval instrument 100, 200, 300, 400. Flexibility of the cannula 120,220, 320, 420 and/or the rotation mechanism 140, 240, 340 can be used toprovide steering/directional control when accessing the target area andduring removal of tissue.

One or more components of the material removal instrument 100, 200, 300,400 may be made from any biocompatible material known including, forexample, metals such as titanium, titanium alloys, stainless steel andcobalt chromium, cobalt chromium molybdenum (CoCrMo), or other metals.Other materials include, for example, composites, polymers, or ceramics.In one example, one or more components of the material removalinstrument 100, 200, 300, 400 can be constructed from a radiopaquematerial including, for example, stainless steel such as 17-4PHstainless steel. Likewise, one or more components described herein canbe constructed from a radiolucent material to enhance visibility of theassembly during radiographic imaging. Example radiolucent materials caninclude “life science” grade PEEK (Ketron 450G PEEK). Life science gradePEEK can improve wear and abrasion characteristics as well as providehigh yield strength. A coating may be added or applied to the variouscomponents described herein to improve physical or chemical properties,such as a plasma-sprayed titanium coating or Hydroxypatite. Moreover,skilled artisans will also appreciate that the various components hereindescribed can be constructed with any dimensions desirable forimplantation and cavity creation.

While the foregoing description and drawings represent the preferredembodiment of the present invention, it will be understood that variousadditions, modifications, combinations and/or substitutions may be madetherein without departing from the spirit and scope of the presentinvention as defined in the accompanying claims. In particular, it willbe clear to those skilled in the art that the present invention may beembodied in other specific forms, structures, arrangements, proportions,and with other elements, materials, and components, without departingfrom the spirit or essential characteristics thereof. One skilled in theart will appreciate that the invention may be used with manymodifications of structure, arrangement, proportions, materials, andcomponents and otherwise, used in the practice of the invention, whichare particularly adapted to specific environments and operativerequirements without departing from the principles of the presentinvention. In addition, features described herein may be used singularlyor in combination with other features. The presently disclosedembodiments are, therefore, to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims and not limited to the foregoingdescription.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention, as defined by the following claims.

What is claimed is:
 1. A material removal instrument, comprising, acannula including: a cannula bore; and a cannula opening at a distal endof the cannula, the cannula opening providing access to the cannulabore; and a rotation mechanism disposed at least partially within thecannula, the rotation mechanism including: an elongated shaft having acentral bore and an opening at a distal end of the elongated shaftproviding access to the central bore; projections extending from aportion of the elongated shaft; a blade extending from an other portionof the elongated shaft for dislocating material from a target area, atleast a portion of the blade extends from the cannula opening; whereinthe rotation mechanism is rotatable within the cannula to cause theblade to dislocate material from the target area, wherein the dislocatedmaterial is drawn from the target area through the cannula bore.
 2. Thematerial removal instrument of claim 1, wherein the cannula opening islocated on an end wall of the cannula.
 3. The material removalinstrument of claim 1, wherein the cannula opening is located on alateral surface of the cannula.
 4. The material removal instrument ofclaim 1, wherein the projections form a helical surface extending aroundthe elongated shaft.
 5. The material removal instrument of claim 1,wherein the central bore of the rotation mechanism is operativelycoupled to an irrigation source.
 6. The material removal instrument ofclaim 1, wherein the central bore of the rotation mechanism is sized andconfigured to receive a guide wire.
 7. The material removal instrumentof claim 1, wherein a proximal end of the rotation mechanism isoperatively coupled to a source of rotational energy.
 8. The materialremoval instrument of claim 1, wherein the blade extends in a radialdirection from the elongated shaft.
 9. The material removal instrumentof claim 1, wherein the blade extends from the distal end of theelongated shaft.
 10. The material removal instrument of claim 1, whereina portion of the blade includes a surface that forms a helical surfaceextending around a longitudinal axis of the elongated shaft.
 11. Thematerial removal instrument of claim 9, wherein a height defined by thediameter of the rotated blade is generally constant during rotation. 12.A material removal instrument, comprising, a cannula including: acannula bore; and a cannula opening at a distal end of the cannula, thecannula opening providing access to the cannula bore; and a rotationmechanism disposed at least partially within the cannula, the rotationmechanism including: an elongated shaft; a thread extending from aportion of the elongated shaft for dislocating material from a targetarea, the thread including a flank having a leading side and a trailingside, the trailing side having a flank angle less than 90° with respectto a longitudinal axis of the rotation mechanism; wherein at least aportion of the rotation mechanism extends from the cannula opening,wherein the rotation mechanism is rotatable within the cannula to causethe thread to impact and dislocate material from the target area. 13.The material removal instrument of claim 12, wherein the dislocatedmaterial is urged from the target area through the cannula bore byrotation of the thread.
 14. The material removal instrument of claim 12,wherein the cannula opening is located on a lateral surface of thecannula.
 15. The material removal instrument of claim 12, wherein thethread forms a helical thread around an outer surface of the portion ofthe elongated shaft.
 16. The material removal instrument of claim 12,wherein the thread includes a plurality flanks, wherein a pitch betweena first set of flanks varies from a pitch between a second set offlanks.
 17. The material removal instrument of claim 12, wherein thethread includes a plurality of flanks, wherein a height of a first flankvaries from a height of a second flank.
 18. The material removalinstrument of claim 17, wherein an overall height of the plurality offlanks increases from a distal end to a proximal end of the rotationmechanism.
 19. A material removal instrument, comprising, a cannulaincluding: a cannula bore; and a cannula opening at a distal end of thecannula, the cannula opening providing access to the cannula bore; and arotation mechanism disposed at least partially within and rotatablewithin the cannula, the rotation mechanism including: an elongatedshaft; a connection element fixed to the elongated shaft; and a masselement for dislocating material from a target area, the mass elementfixed to the connection element, wherein rotation of the rotationmechanism causes the connection element to move in a direction away froma longitudinal axis of the rotation mechanism and causes the masselement to rotate about the longitudinal axis of the rotation mechanismat a distance from the longitudinal axis. wherein rotation of the masselement causes the mass element to impact and dislocate material fromthe target area.
 20. The material removal instrument of claim 19,wherein the connection element is a flexible wire.
 21. The materialremoval instrument of claim 19, wherein the mass element includes acutting surface.
 22. A material removal instrument, comprising, acannula including: a cannula bore; and a cannula opening at a distal endof the cannula, the cannula opening providing access to the cannulabore; and a cutting element disposed at least partially within thecannula, the cutting element attached to an inner element, wherein thecutting element expands radially from the cannula opening upon movementof the inner element from a first position to a second position in adirection along a longitudinal axis of the cannula, wherein rotation ofthe cannula with the cutting element in the expanded position causes thecutting element to impact and dislocate material from a target area. 23.The material removal instrument of claim 21, wherein the cutting elementcomprises a flexible blade.
 24. The material removal instrument of claim21, wherein the inner element can be rotated with respect to the cannulacausing the cutting element to rotate forming a spiral cutting surfaceabout the a longitudinal axis of the inner element.